This invention relates to a gas drying apparatus and more specifically to a twin tower gas drying apparatus.
The presence of moisture in gases leads to difficulties in many industries and operations. With a slight drop in temperature, condensation can occur in pipelines and reservoirs which can lead to corrusion, scales, freeze-ups, dirt, etc. which may damage instruments and controls and cause blockages in airlines, produce excessive pressure drops, increase down-time and reduce the life of tools. Similarly in chemical, food and metal working industries, the presence of moisture in the air and gases produces undesired oxidation. It has also been found that the robotics field requires extremely dry air for the operation of its pneumatic systems.
In order to produce extremely dry air i.e., dew points of minus 40.degree. Farenheit or lower, it is necessary to use an adsorptive drying system. Typically, adsorption drying is done by means of twin towers filled with a desiccant. The basis for the twin tower adsorption method is that while one tower is receiving moisture laden air for drying, the other tower is having its desiccant regenerated by passing dry air through that tower. In the past, this regeneration process has been accomplished by taking a portion of the dry air exiting the tower in the drying cycle and passing this air through the other tower to absorb moisture from the desiccant in that tower and thus regenerate that desiccant. Typically, 15% of the dry air exiting the tower in the drying cycle is utilized to regenerate the other tower. This method has the obvious disadvantage of diverting 15% of the dry air away from its end use in order to utilize it for regenerating one of the towers. Therefore, it is desirable to have a system that could reduce the amount of dry air needed to regenerate the towers to an amount that is considerably less than 15%.